1. Field of the Invention
The present invention relates to a display device made of plural display tubes each of which can emit light partially.
There is a limit to enlarge screen size of a display made of one unit. Therefore, an array type large display in which multiple display tubes are arranged is under development for commercialization.
2. Description of the Prior Art
This type of large display is disclosed in Japanese unexamined patent publication No. 2000-315460. In this publication, FIGS. 15 and 17 show a display device that is made of multiple display tubes arranged in parallel and a substrate for supporting the display tubes. Each display tube includes a glass tube containing discharge gas, strap-like main electrodes (for displaying) arranged on the outer surface of the glass tube along the length direction and a longitudinal sub electrode (for addressing) arranged inside the glass tube so as to cross all the main electrodes. Two main electrodes neighboring with a predetermined gap make an electrode pair for surface discharge. On the substrate, band-like bus electrodes (power supplying conductors) are arranged so as to cross the sub electrode, and the display tube is arranged on the substrate so that the main electrode abuts the bus electrode. The bus electrode makes electric connection among the main electrodes of all the display tubes at the same position in the length direction. Namely, the bus electrode group and the sub electrode group form an electrode matrix. A potential control of the electrode matrix is performed so that any desired image can be displayed.
By forming the main electrodes on each of the display tubes, an area where surface discharge is generated (i.e., a position of a discharge portion) can be determined easily. Furthermore, by forming a bus electrode on the substrate, the electrode matrix can be formed much more simply compared to the case where the main electrodes are connected by printing a conductive paste on the display tubes after arranging the display tubes.
Conventionally, there is a problem that the process for manufacturing the display tube is complicated and that the connection of the sub electrode to the driving circuit is difficult since the sub electrode for forming an electrode matrix with the bus electrode is located inside each of the display tubes.
An object of the present invention is to simplify the structure of the display tube so as to realize cost reduction and to make connection with a driving circuit easy.
The present invention provides a display device having a structure in which a group of display tubes arranged in parallel are sandwiched between a front substrate and a back substrate, and band-like conductors for forming an electrode matrix are arranged on both the substrates. An auxiliary electrode for display is formed on the display tube so that the position of the discharge portion is determined.